Thermostatic switch



March 22 1932- J. A. SPENCER I THERMQSTATIC SWITCH Filed Feb. 16, 1931 3 of relatively high coefficient of Patented Mar. 22, 15932 UNITED STATES PATENT oFFlcE JOHN A. SPENCER, NEWTONVILIE, MASSACHUSETTS, ASSIGNOB TO GENERAL PLATE COMPANY, OF ATTLEBORO, MASSACHUSETTS, A CORPORATION 0F MASSACHUSETTS TnERntos'rA'rIc SWITCH Application led February 16,1931r Serial No. 516,044.

This invention relates to thermostats, and with regard to certain more specific features, to thermostats in which relatively slow moving thermal elements drive an overcentering (device through a suitable connecting linkage.

Among the several objects of the invention may be noted the provision of apparatus of the class set out in which said connecting linkage is positively limited in its movement to a predetermined amount, so that the overcentering device will not be injured by excessive vtemperature change, yet which does not subject said linkage to stresses which are above its elastic limit. Other objects will be in part obvious and in part pointed out hereinafter.

The invention is an improvement upon the invention set out in my copendlng United States patent application, Serial No. 479,859,11ed Sept. 5, 1930.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplied in the structure hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which are illustrated two of various possible embodiments oithe invention,

Fig. l is a cross section showing the invention;

Fig. 2 is a cross section, on a reduced scale, taken on line 2 2 of Fig.' l; and,

Fig. 3 is a detail showing an alternative form of the invention.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

l Referrin now more particularly to Fi 1, there is s own at numeral 1 abody to whic is affixed at one of its ends a metal cylinder thermal expansion. The other end of the cylinder 3 is made fast (as at 5) to a stem 7 of relatively lower coeiiicient of expansion. The rod or stem 7 passes through the cylinder or pipe 3 and through the body 1. From this, it 'will be seen that if the temperature of the members beyond its elastic 3, 7 be changed, the former will change length faster than the latter and cause the uniixed end 9 oi' the rod 7 to move.

It is desirable that said motion be transmitted and preferably multiplied in trans- .for transmitting movement from the end 9 ofthe rod 7 to the switch 13. 1t was pivoted on one side of therod 7 and pressed against the button 11 on the other side, the rod 7 engaging in between, whereby motion was transmitted. A limiting stop was put on the lever to prevent unlimited movement against the button 11, thus eliminating the possibility of breaking the switch 13 by excessive movement of the arts thereof. But there remained the possi ility of straining the lever limit by excessive motion of the rod 7, in turn caused by excessive heatinc of the device.

overcome the above diculties by fastening a spring or resilient arm 17 to the body l and extending from one side of the rod 7. This spring arm 17 arches over the end 9 of the rod 7 and reaches to the button 11 which it tends to press inwardly against the lighter action of spring 15. Normally it is prevented from pressing the button 11 and thus moving the switch 13, this being done by Contact underneath the spring 17 of the rod 7, which, in its cold position is extended' a greater amount fromfthe tube 3 than in its hot position.- Upon heating, the rod 7 retracts and permits the leaf'spring 17 to travel away from its strained position in which it was held by the rod 7, and thus toward the switch button 11 to press the same against the reaction of spring 15. 'llhus heating effects movement of the barrier comprising rod 7 so that the initially strainedy spring 17 may move. t

forced lagainst the spring 17 to bend the same outward so as to release the button 11, thus permitting ,the spring 15 to move the switch in reverse direction. v

A suitable centering and anti-friction bearing-19 is placed between the leaf spring 17 and' the rod 7.

It is to be understood that the principles herein set out may -be applied to thermostats operatinglto open the switch upon heating or to close t e same upon heating, or'operating other devices such as valves and the like instead of switches, for broadly, the invention comprises stressing'the spring when the thermal elements are in normal position and when said elements are in abnormal positions, permitting^the spring to relieveitself of stresses and thus do work. `Furthermore, the normal flexure of the spring when released is such that the switchor element to be moved is not driven beyond its. limits.

At numeral 2 is shown a lever or'adjusting the threading ofthe tube 7, into the body 1 to change the temperature at which the device will throw, the tube 3 being threaded into the body 1. I n Fi 3- is shown a springless type of button 11 w erein a direct attachment is 'made to the end of the leaf spring 17 so that not only does the action of the sprin 17 move the switch 13 in one direction, gut the return movement of spring 17 (caused by pressure from rod 7 upon cooling) draws the switch to its opposite position. It is possible thatexcessive cooling` might cause the spring 17 Vto pull the switch too far in the outward direction but this is a most'remotecontingency. Furthermore, the preferred form provides against it, because it will be seen that the spring 17-may leave the button 11 (Fig. 1).

It may be noted that adjustment for temv fperature of operation may be made by loosenin the lock nut 8 and' screwing in or out the. tu e 3.

In igiew of the above, it will be seen that the several ob'ects of the invention are achieved and ot er advantageous results attained.

As many changes could be made in carrying out the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limitingsense.

I claim: 1. A thermostatl comprising relatively L to be moved, a spring normally strained and movable thermal elements,\a member adapted consequently stressed by said thermal elements and engaging the member to be moved, said thermal elements being adapted to release said sprin upon temperature change,

whereby the spring relieves at least some of its stresses b returning toward its unstrained position an causing operation of said mem- 2. A thermostat comprising relatively movable thermal elements, a member adapted to be moved, a spring normally strained and' consequently stressed by said thermal elements and engaging the member to be moved, said thermal elements being adapted to release said spring upon temperature change, whereby the spring relieves at least some of its stresses by returning toward its unstrained position and causing operation of said member,said spring having a lost-motion connec-r tion with the thermal elements.

3. A thermostat comprising relatively movable thermal elements, a member adapted to bemoved, a spring normally strained and consequently stressed -by said thermal elements and engaging the member to be moved, said thermal elem-ents being adapted to release said spring upon temperature change, whereby the spring relieves at least some of its stresses b returning toward its unstrained position an causing operation of said member, said spring having a lost-motion connection with the thermal elements and means for resetting said moved member when said thermal elements are'again in normal position.

4. A thermostat comprising relatively movable thermal elements, a member' adapted to bemoved, a spring normally strained and consequently stressed by said thermal elements and engaging themember to be moved, said thermal tlements being adapted to release said spring upon temperaturechange,

av positive attachment between1 said spring and the moved member, whereby the latter is reset when said thermal elements are again innormal position.

5; A thermostat comprising relatively movable thermal elements, a member adapted to be moved, a spring normally-strained and consequently stressed by said thermal elements and engaging the member to be moved, said thermal elements being adapted to release said spring upon temperature change, whereby the spring relieves at least some of its stresses by returning toward its unstrained position and causing operation of said member, said sprin having a lost-motion connection with the t ermal elements, the inal position of the spring being substantially unstrained when lost-motion occurs at said attachment.

6. A4 thermostat comprising relatively movable thermal elements, a member adapted to be moved, a springY normally strained and consequently stressed by said thermal elements and engaging the member to bemoved,

said thermal elements being adapted to release said spring upon temperature change whereby the spring relieves at least some of its stresses by returning toward its unstrained position and causing operation of said member, said spring having a lost-motion connection with the thermal elements, the nal position of the spring being substantially unstrained when lost-motion occurs at said attachment, and said lost-motion occurring only under substantial abnormal movements of said thermal elements.

7 A thermostat comprising relatively movable thermal elements, a member adapted to be moved, a sprin normally strained and consequently stresse by said thermal elements and engaging the member to be moved, said thermal elements being adapted to release said spring upon temperature change whereby the spring relieves at least some of its stresses by returning toward its unstrained position and causing operation of said member, said spring having a lost-motion connection with the thernal elements,

. the iinal position of the spring being substanlease said resilient means upon temperature change, whereby said resilient means relieves at least some of its stresses by returning toward it unstrained position and causing operation of said member.

In testimony whereof, I have signed m name to this specification this 30th. day of January, 1931.

JOHN A. SPENCER.

' CERTIFICATE 0F CORRECTION.

Patent No. 1,850, 360. March 22, 1932.

JOHN A. SPENCER.

It is hereby certified that error appears inthe printed specification of -lhe above' numbered pim-m requiring correction as follows: Page 2, line 59, claim 1, .strike out the words "to be moved, a spring normally strained and" and insert them after line 60, of same claim; and line/100, claim` 4, for "tlem'ems" read elements; and that the .said Letters Patent should, be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of October, A. 1934.

Leslie Frazer (Seal) Acting Commissioner of Patents. 

